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The degradation of trees at the edges of tropical forests is more widespread than previously thought, according to new research.

The study, published in Nature, explains that trees near deforested or degraded areas of the forest are more vulnerable to drought, as well as to human activity such as logging. These “edge effects” are measurable up to 1.5km into the forest, the authors find.

This is an “amazing result”, a study author tells Carbon Brief, because previous studies detected these effects only within the first 120 metres of the forest edge. The new figure indicates that 18% of the remaining tropical moist forests are impacted by edge effects – an area more than 200% larger than previously estimated.

Experts not involved in the study tell Carbon Brief that quantifying tropical forest degradation is “frustratingly elusive”. And while some praise the methods used in the paper, others advise caution when interpreting the conclusions.

Two Brazilian scientists also tell Carbon Brief that the study overlooks important work from institutions in the global south who are also working on this problem. They advise that scientists from local groups should be invited to contribute to research in this area.

Forest height

Tropical forests account for around 45% of forest cover globally. These forests are well-known for their high biodiversity and the crucial ecosystem services that they provide. They also hold around one-quarter of all land-based carbon. 

The new study assesses how deforestation and degradation affect “moist tropical forests” – tropical forests in the equatorial belt with a fairly consistent annual temperature and high levels of rainfall. Tropical dry forests and deciduous forests are not included in the analysis.

Research shows that around 17% of tropical moist forests disappeared over 1990-2021, largely due to human activity such as logging and fires. Of the 1,071m hectares that remained globally in 2019, around 10% were degraded, the new study says. This means that they suffered human-induced “disturbances” that led to a partial loss of their tree cover or function.

Furthermore, trees at the edges of tropical forests have higher mortality rates than trees in the centre, because they are more exposed to disturbances such as fire and drought. When intact forest landscapes become fragmented – for example, due to logging, fire, drought or the construction of roads into the forest – these “edge effects” can lead to further forest degradation.

The authors use data collected by the Global Ecosystem Dynamics Investigation (GEDI) instrument on the International Space Station to assess the forest structure – such as canopy height and aboveground biomass – over the past four years. 

To measure canopy height, the authors calculate the “RH98” value – the height of the top of the canopy or the nearest tallest vegetation in the area. This is an important measure of forest health and maturity. Aboveground biomass measures the aboveground woody biomass per unit area and is also a good measure of forest health.

They combine this with data from the Tropical Moist Forest dataset, which uses Landsat satellite imagery to show how tropical moist forests have changed over 1990-2022.

The plot below shows the canopy height for different types of moist tropical forests. The rows show intact forests at least 3km from a forest edge (top row), degraded forests (second row), the edges of forests (third row) and forest regrowth (bottom row), as shown in the maps below.

Darker blues indicate taller forest canopies. The map shows where the forests are located, and the bar charts on the right hand side show the overall distribution of different tree heights.

Canopy height for moist tropical forests for intact forests (top row) degraded forests (second row), the edges of forests (third row) and forest regrowth (bottom row), as shown in the maps below.
Canopy height for moist tropical forests for intact forests (top row) degraded forests (second row), the edges of forests (third row) and forest regrowth (bottom row), as shown in the maps below. Dark blue indicates a taller area of the forest and light blue indicates a shorter area. The map shows the distribution of trees and the bar charts on the right-hand side show the frequency. Source: Bourgoin et al (2024)

The tallest intact moist tropical forests are found in south-east Asia, where the average canopy height is 34m, the study finds. West and central Africa and Central and South America have average forest heights of 29m. This is because intact tropical forests in Asia, which are typically dominated by “hardwood wind-dispersed species”, are typically taller, the authors say.

The map also shows that degraded forests, forest edges and areas of forest growth have a greater proportion of shorter trees on average.

The forest edge

The study investigates two different types of forest edge effects, exploring how areas of deforested and degraded land impact nearby trees.

Dr Lilian Blanc is an author on the study and researcher at the French Agricultural Research Centre for International Development. He tells Carbon Brief that the effect of nearby degraded land “was not considered in previous studies”.

The graphs below show how areas of deforested land affect tree canopy height. The charts at the top show the average distribution of canopy heights of undisturbed forests in the Americas, Africa and Asia. The line colours indicate the distance of those trees from the forest edge, with yellow indicating a short distance and blue indicating a large distance.

The bottom map shows how far into the forest edge effects are present, by measuring the distance from the forest edge at which the height of the forest reaches 95% of the height of the intact, undisturbed forest. 

Average distribution of canopy heights of undisturbed forests at different distances from the forest edge (top) in the Americas, Africa and Asia, and the distance at which the forest height drops to 95% of the height of the intact forest (bottom).
Average distribution of canopy heights of undisturbed forests at different distances from the forest edge (top) in the Americas, Africa and Asia, and the distance at which the forest height drops to 95% of the height of the intact forest (bottom). Yellow indicates a short distance to the forest edge, and blue indicates a high distance. Source: Bourgoin et al (2024)

The authors find the greatest edge effects from deforestation along the “forestation fronts of the Amazon”, in Borneo and Sumatra coasts marked by high fragmentation levels, and on the borders of the Congo basin.

They also record a decrease in canopy height up to 350, 400 and 1,500 metres from the deforested edge in the Americas, Africa and Asia, respectively.

The authors find that within 120 metres of trees that have been degraded due to logging and burning, the average canopy height in undisturbed forests is 15% and 22% lower, respectively.

The authors also investigate how quickly the forest can recover from logging and fires, concluding that while there is “fast regrowth of pioneer and understory species”, there is “no significant recovery in canopy height in the 30 years following the creation of a forest edge”.

Forest degradation can also increase the likelihood of deforestation, the authors say. They warn that forest height and distance to the edge of the forest are “strong predictors of deforestation”, as forest fragmentation makes the interior of the forest more accessible to loggers.

It adds that there has been selective logging 500 metres from the forest edge in Africa and the Americas, and even deeper in Asia.

Agriculture and road expansion trigger a 20-30% reduction in canopy height and biomass at the forest edge, with “persistent effects” measurable up to 1.5km inside the forest, the authors find. Blanc tells Carbon Brief that this is “an amazing result” as previous studies only looked for edge effects up to 120 metres from the forest edge.

The authors also calculated the edge effect using total above ground woody biomass, instead of canopy height. Using this metric, the authors conclude that the total area of forest with this edge effect is 18% of total global forest area in 2022 – an area more than 200% larger than previously estimated.

Prof Simon Lewis – a professor of global change science at University College London’s department of geography – tells Carbon Brief that this is a “striking new result”. 

It implies that “the negative impacts on remaining forest from the creation of forest edges are much more extensive than has been commonly documented”. It also means that “forest protection of large blocks of forest is going to be more important than we previously thought”, he says.

Overall, the study is “an important step forward in monitoring forest disturbance, which is a very tough problem”, Lewis says. However, he adds that “care is needed” when looking at some of the observational data, saying that he “trust[s] the broad patterns of biomass loss following logging, edge creation and fires, but not the specific biomass loss values from these disturbances”.

Dr Peter Potapov – a researcher in the department of geographical sciences at the University of Maryland, whose work was cited extensively in the new study – says “the conclusion that edge effects are degrading 18% of the remaining humid tropical forest is an overstatement”.

He says that forest degradation depends on other factors, such as land-use regulations, and argues that “the assumption that all forests 1.5km away from the edges are degraded may undermine ongoing conservation efforts.

Expert response

These comments reflect the mixed response that the new study has received.

Prof Matthew Hansen – a remote sensing scientist at the University of Maryland’s department of geography – tells Carbon Brief that forest degradation is “a frustratingly elusive dynamic to quantify”. However, he praises the study for being “very clear and ambitious”. 

Potapov, who has published research with Hansen, tells Carbon Brief that the results broadly confirm existing findings, but warns that there are some “major limitations” with the study.

For example, he says the method does not include a “matching technique” to separate the effect of human management on tree height from the natural factors such as elevation, soil quality and floods. He also warns that the observations “failed to correctly map anthropogenic disturbances in humid tropical forests”, adding:

“The authors greatly underestimate selective logging in Gabon, while the natural non-fire disturbances like river meandering and windfalls in South America were probably treated as human-caused degradation.”

Dr Flávia de Souza Mendes, a programme manager in forest and land use at satellite imagery firm Planet Labs, says the study is “well written”. However, she laments that “there are several local groups from the global south that have been studying this topic and are not part of this study”. She suggests that scientists carrying out similar studies should “invite more local researchers to take part”.

She also tells Carbon Brief that this paper “did not take into account studies carried out by local researchers on the relationship between degradation and deforestation”.

For example, she highlights a report by Brazilian researchers which finds that, in some regions of the Amazon, 86% of degraded areas were not subsequently cleared in the following decades. This is not in line with the findings of the new study, where degradation “has a crucial role in predicting future deforestation”, she says.

Prof Celso Silva-Junior – a research scientist in amazon ecology and remote sensing at Brazil’s Universidade Federal do Maranhão – tells Carbon Brief that the study “reproduces the findings of our research group, which has been investigating large-scale forest edge effects, using remote sensing technologies, since 2016”.

He says that the paper’s findings concerning biomass loss beyond 120 metres from the forest edge are “critical”. However, he emphasises the importance of the “local knowledge of tropical scientists” who are “deeply involved in the establishment of the conceptual framework for treating this relevant problem”.

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Tropical forest degradation due to ‘edge effects’ is 200% higher than thought

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Indigenous groups warn Amazon oil expansion tests fossil fuel phase-out coalition

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Indigenous leaders from across the Amazon have warned that stopping the expansion of oil drilling into their territories will be a crucial test for a growing international coalition committed to transitioning away from fossil fuels.

As 60 countries discussed at a landmark conference in Santa Marta, Colombia, pathways to end the world’s reliance on fossil fuels, Indigenous groups said the process risks losing credibility if governments continue opening new oil frontiers in the Amazon.

Their central demand was the establishment of fossil fuel “exclusion zones” across Indigenous territories and biodiverse areas of the rainforest, permanently barring new oil and gas expansion in one of the world’s most critical ecosystems. Indigenous representatives proposed establishing protected “Life Zones”, which they said would provide legal safeguards against governments and companies seeking to expand extraction into their lands.

But Indigenous delegates left the conference frustrated as the final synthesis report drafted by co-chairs Colombia and the Netherlands failed to include the proposal.

In a statement at the end of the conference, Patricia Suárez, from the Organization of Indigenous Peoples of the Colombian Amazon (OPIAC), said formally declaring Indigenous territories – especially those inhabited by peoples in voluntary isolation – as exclusion zones for extractive industries was “an urgent measure”.

“If the heart of the conference does not begin there, it risks remaining a set of good intentions that fails to respond to either science or our Indigenous knowledge systems,” she added.

Pushing for a new oil frontier

Campaigners say the pressure on the Amazon is intensifying just as scientists warn the rainforest is nearing irreversible collapse. Around 20% of all newly identified global oil reserves between 2022 and 2024 were discovered in the Amazon basin, fuelling renewed interest from governments and companies seeking to develop the region as the world’s next major oil frontier.

Ecuador has moved ahead with the auction of new oil blocks in the rainforest, while the country’s right-wing president Daniel Noboa has promoted the region as a “new oil-producing horizon” and backed efforts to expand fracking with support from Chinese companies.

    In Santa Marta, a coalition of seven Indigenous nations from Ecuador issued a declaration condemning the government, which did not participate in the conference.

    “While the world talks about energy transition, our government is pushing for more oil in the Amazon,” said Marcelo Mayancha, president of the Shiwiar nation. “Throughout history, we have always defended our land. That is our home. We will forever defend our territory.”

    Indigenous groups also warned that Peru – another South American nation absent from the conference – plans to auction new oil blocks in the Yavarí-Tapiche Territorial Corridor, a highly sensitive region along the Brazilian border that contains the world’s largest known concentration of Indigenous peoples living in voluntary isolation.

    COP30 host under scrutiny

    Indigenous leaders also criticised Brazil, arguing that despite its international climate leadership, the country is simultaneously advancing major new oil projects in the Amazon region.

    Luene Karipuna, delegate from Brazil’s coalition of Amazon peoples (COIAB), said the oil push threatens the stability of the rainforest. Not far from her home, in the northern state of Amapá, state-run oil giant Petrobras is currently exploring for new offshore oil reserves off the mouth of the Amazon river.

    Brazil participated in the Santa Marta conference and was among the countries that first pushed for discussions on transitioning away from fossil fuels at COP negotiations. Yet the country is also planning one of the largest expansions in oil production in the world, according to last year’s Production Gap report.

    Veteran Brazilian climate scientist Carlos Nobre told Climate Home that the country’s participation at the Santa Marta conference contrasted with its oil and gas production targets. “It does not make any sense for Brazil to continue with any new oil exploration,” he said, and noted that science is clear that no new fossil fuels should be developed to avoid crossing dangerous climate tipping points.

    He added that the Brazilian government faces pressures from economic sectors, since Petrobras is one of the countries top exporting companies. “They look only at the economic value of exporting fossil fuels. Brazil has to change.”

    The COP30 host also promised to draft a voluntary proposal for a global roadmap away from fossil fuels, which is expected to be published before this year’s COP31 summit.

    “In Brazil, that advance has caused so many problems because it overlaps with Indigenous territories. Companies tell us there won’t be an impact, but we see an impact,” Karipuna said. “We feel the Brazilian government has auctioned our land without dialogue.”

    For Karipuna and other Indigenous leaders, establishing exclusion zones across the Amazon is no longer just a regional demand, but a prerequisite to prevent the collapse of the rainforest.

    “That’s the first step for an energy transition that places Indigenous peoples at the centre,” she added.

    The post Indigenous groups warn Amazon oil expansion tests fossil fuel phase-out coalition appeared first on Climate Home News.

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    Kenya seeks regional coordination to build African mineral value chains

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    African leaders have intensified calls for governments to stop exporting raw minerals and step up efforts to align their policies, share infrastructure and coordinate investment to add value to their resources and bring economic prosperity to the continent.

    In a speech to the inaugural Kenya Mining Investment Conference & Expo in Nairobi this week, Kenyan President William Ruto became the latest African leader to confirm the country will end exports of raw mineral ore. The East African nation has deposits of gold, iron ore and copper and recently launched a tender for global investors to develop a deposit of rare earths, which are used in EV motors and wind turbines, valued at $62 billion.

    Kenya is among more than a dozen African nations that have either banned or imposed export curbs on their mineral resources as they seek to process minerals domestically to boost revenues, create jobs and capture a slice of the industries that are producing high-value clean tech for the energy transition.

      “For too long we have extracted and exported raw materials at the bottom of the value chain, while others have processed, refined, manufactured and captured the greater share of economic value,” Ruto told African ministers and stakeholders gathered at the mining investment conference in Nairobi.

      As a result, Africa currently captures less than 1% of the value generated from global clean energy technologies, he said. To address this, Kenya, in collaboration with other African nations, “will process our minerals here in the continent, we will refine them here and we will manufacture them here”, he added.

      Mineral export restrictions on the rise

      Africa is a major supplier of minerals needed for the global energy transition. The continent holds an estimated 30% of the world’s critical mineral reserves, including lithium, cobalt and copper. The Democratic Republic of Congo produces roughly 70% of global cobalt, a key ingredient in lithium-ion batteries, while countries such as Guinea dominate bauxite production, and Mozambique and Tanzania hold significant graphite deposits.

      But African governments have struggled to attract the investment needed to turn their vast mineral wealth into a green industrial powerhouse. Recently Burundi, Malawi, Nigeria and Zimbabwe are among those that have resorted to banning the export of unrefined minerals to incentivise foreign companies to invest in value addition locally.

      Outdated geological data limits Africa’s push to benefit from its mineral wealth

      This week, Zimbabwe exported its first shipments of lithium sulphate, an intermediate form of processed lithium that can be further refined into battery-grade material, from a mine and processing plant operated by Chinese company Zhejiang Huayou Cobalt.

      After freezing all exports of lithium concentrate – the first stage of processing – earlier this year, the government introduced export quotas and will ban all exports from January 2027.

      Export restrictions on critical raw materials have grown more than five-fold since 2009, found a report by the Organisation for Economic Co-operation and Development (OECD) published this week. In 2024, a more diverse group of countries, including many resource-rich developing economies in Africa and Asia, introduced restrictions, including Sierra Leone, Nigeria and Angola.

      This is “a structural shift in the wrong direction,” Mathias Cormann, the OECD’s secretary-general, told the organisations’ Critical Minerals Forum in Istanbul, Turkey, this week.

      “We understand the motivations: building local industries, managing environmental impacts, capturing greater value domestically. But our research is quite clear. Export restrictions distort investment, reduce volumes and undermine supply security often while delivering limited gains in value added,” he said.

      In-country barriers to success

      Thomas Scurfield, Africa senior economic analyst at the Natural Resource Governance Institute, told Climate Home News that export restrictions “can look like a promising route to local value addition” for cash-strapped African mineral producers but have “rarely worked” unless countries already have reliable energy, infrastructure and competitive costs for processing.

      “Without those conditions, bans may simply push companies to scale back mining rather than scale up processing,” he said.

      Alaka Lugonzo, partnerships lead for Africa at Global Witness, identified gaps in practical skills and infrastructure as other major barriers. “You need engineers, geologists, marketers,” Lugonzo said, warning that graduates are increasingly unable to match the pace of industry change.

      On infrastructure, she said that plentiful and stable energy supplies are vital and while Kenya has relatively robust road networks, they are insufficient for industrial-scale operations.

      “Meaningful value addition and real industrialisation requires heavy machinery… and you will need better infrastructure,” she said, highlighting persistent last-mile challenges in mining regions where “there’s no railway, there’s no electricity, there’s no water”.

      Export capacity is another concern, she said, particularly whether existing port systems could handle increased volumes of processed minerals.

      Regional approach recommended

      Scurfield said that through regional cooperation – including pooling supplies, specialising across different stages of refining and manufacturing, and building larger regional markets – “African countries could overcome many domestic constraints that make going alone difficult”.

      That’s what close to 20 African governments are working to deliver as part of the Africa Minerals Strategy Group, which was set up by African ministers and is dedicated to foster cooperation among African nations to build mineral value chains and better benefit from the energy transition.

      Africa urged to unite on minerals as US strikes bilateral deals

      Nigerian Minister of Solid Minerals Dele Alake, who chairs the group, said “true collaboration” between countries, including aligning mining policies, sharing infrastructure, coordinating investment strategies and promoting trade across the continent, will create the conditions for long-term investments that could turn Africa into “a formidable and competitive force within the global mineral supply chain”.

      “The time has come for Africa to redefine its place within the global mineral economy and that transformation must begin with regional integration and regional cooperation,” he told the mining investment conference in Nairobi.

      Lugonzo of Global Witness agreed, saying that value-addition would benefit from adopting a continental perspective. “Why should Kenya build another smelter when we can export our gold to Tanzania for smelting, and then we use the pipeline through Uganda to take it to the port and we export it?” she asked.

      To facilitate that, there is a need to operationalise the Africa Free Trade Continental Agreement (AFTCA), she added. “That agreement is the only way Africa is going to move from point A to point B.”

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      Key green shipping talks to be held in late 2026

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      The future of the global shipping industry – and its 3% share of global emissions – will be decided in three weeks of talks in the third quarter of this year, after a decision taken in London on Friday.

      At the International Maritime Organisation (IMO) headquarters this week, governments largely failed to substantively negotiate a controversial set of measures to penalise polluting ships and reward vessels running on clean fuels known as the Net-Zero Framework. The green shipping plan has been aggressively opposed by fossil fuel-producing nations, in particular by the US and Saudi Arabia.

      This week, countries delivered statements outlining their views on the measures in a session that ran from Wednesday into Thursday. Then, late on Friday afternoon, they discussed when to negotiate these measures and what proposals they should discuss.

      After a lengthy debate, which the talks’ chair Harry Conway joked was confusing, governments agreed to hold a week of behind-closed-door talks from 1 September to 4 September and from 23 November to 27 November.

      Following these meetings, which are intended to negotiate disagreements on the NZF and rival watered-down measures proposed by the US and its allies, there will be public talks from November 30 to December 4.

        Last October, talks intended to adopt the NZF provisionally agreed in April 2025 were derailed by the US and Saudi Arabia, who successfully persuaded a majority of countries to vote to postpone the talks by a year.

        Those talks, known as an extraordinary session, are now scheduled to resume on Friday December 4 unless governments decide otherwise in the preceding weeks. While this Friday session will be in the same building with the same participants as the rest of the week’s talks, calling it the extraordinary session is significant as it means the NZF can be voted on.

        Em Fenton, senior director of climate diplomacy at Opportunity Green said that the NZF “has survived but survival is not a victory” and called for it to be adopted later this year “in a way that maintains urgency and ambition, and delivers justice and equity for countries on the frontlines of climate impacts”.

        NZF’s supporters

        The NZF would penalise the owners of particularly polluting ships and use the revenues to fund cleaner fuels, support affected workers and help developing countries manage the transition.

        Many governments – particularly in Europe, the Pacific and some Latin American and African nations – spoke in favour of it this week.

        South Africa said the fund it would create is “the key enabler of a just transition” and its removal would take away predictable revenues from African countries. Vanuatu said that “we are not here to sink the ship but to man it”.

        Australia’s representative called it a “carefully balanced compromise”, as it was provisionally agreed by a large majority after years of negotiations, and warned that failing to adopt it would harm the shipping industry by failing to provide certainty.

        Santa Marta summit kick-starts work on key steps for fossil fuel transition

        Canada’s negotiator said that if it was weakened to appease its critics like the US and Saudi Arabia, this would disappoint those who think it is too weak already like the Pacific islands.

        A large group of mainly big developing countries like Nigeria and Indonesia did not rule out supporting the framework but called for adjustments to help developing countries deal with the changes. Nigeria called for developing countries to be given more time to implement the measures, a minimum share of the fund’s revenues and discounts for ships bringing them food and energy.

        According to analysis from the University of College London’s Energy Institute, the countries speaking in support of the NZF include five countries which voted with the US to postpone talks in October and a further ten countries which did not take a clear position at that time. Most governments support the NZF as the basis for further talks, the institute said.

        Opposition remains

        But a small group of mainly oil-producing nations said they are opposed to any financial penalties for particularly polluting ships.

        They support a proposal submitted by Liberia, Argentina and Panama which has proposed weakening emission targets and ditching any funding mechanism for the framework involving “direct revenue collection and disbursement”.

        Argentina argued that the NZF would harm countries which are far from their export markets and said concerns over that cannot be solved “by magic with guidelines”. They added that, as a result, the NZF itself needs to be fundamentally re-negotiated.

        The UCL Energy Institute said that just 24 countries – less than a quarter of those who spoke – said they supported Argentina’s proposal.

        While this week’s talks did not see the kind of US threats reported in October, their delegation did leave personalised flyers on every delegate’s desk which were described by academics, negotiators and climate campaigners as misleading.

        One witness told Climate Home News that junior US delegates arrived early on Wednesday and placed flyers behind governments’ name plates warning each country of the costs they would incur if the NZF is adopted.

        The figures on a selection of leaflets seen by Climate Home News ranged from $100 million for Panama to $3.5 billion for the Netherlands. “They are trying to scare countries away from supporting climate action with one-sided information”, one negotiator told Climate Home News.

        A flyer left on Pakistan’s desk, shared by a witness with Climate Home News

        They added that the calculations, by the US State Department’s Office of the Chief Economist, ignore the fact that the money raised would be shared to help poorer countries’ transition as well as ignoring the economic costs of failing to address climate change.

        Tristan Smith, an academic representing the Institute of Marine Engineering, Science and Technology, told the meeting that the calculations were “opaque” and flawed as they overstate the contribution of fuel cost to trade costs.

        A US State Department Spokesperson said in a statement that they “firmly stand behind our estimates” which were shared “in good faith” and to “provide an additional tool to policymakers as they contemplate the true economic burden over the NZF”.

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